The present invention relates to fiber optic communications, and more particularly, to an optical switching device for switching an optical signal in a fiber optic communication system between two or more channels.
Fiber optic cables are used to carry voice, video, and other data signals transmitted as light beams in communications networks. Similar to communication networks using copper wire as the carrier for electronic signals, fiber optic cable lines are interconnected to each other through switches positioned at various locations throughout the communications network. To achieve all-optical routing and rerouting of the communications signals, optical matrix switches or Mxc3x97N crossbar switches are used. All-optical switches should not to be confused with other switching technologies that first convert the optical signals to electrical signals, perform the required routing, and then convert the electrical signals back to optical signals.
As an example of an all-optical switch, U.S. Pat. No. 6,009,219 to Doyle entitled xe2x80x9cOptical Beam Switching Devicexe2x80x9d discloses an optical switching apparatus that uses a solid refractive switching body for selectively coupling first and second optical channels. The solid refractive switching body is moved to position first and second refractive faces adjacent the first and second optical channels.
Another example is U.S. Pat. No. 5,960,132 to Lin entitled xe2x80x9cFiber-Optic Free-Space Micromachined Matrix Switchesxe2x80x9d. Here, an optical switch includes reflective panels which either permit the light beam to travel in a first direction or redirect the light beam from the first direction to a second direction.
However, conventional fiber optic switches may have a low channel density, high insertion loss, static state power consumption and may be relatively bulky. Switching speed, reliability, wavelength range, and cost are other factors that may also be considered depending on the specific application. In particular, the use of wavelength division multiplexing (WDM) is severely straining the capability of conventional switch technology due to the vast increase in the number of channels; and currently no single switch technology is emerging as optimum for all applications. Thus, there is a need for a fiber optic switch with an increase in channel density, a reduced wavelength dependence, a reduction in size, lower insertion loss, higher reliability, and reduced static power consumption.
In view of the foregoing background, it is therefore an object of the invention to increase the channel density, wavelength independence, and reliability of an all-optical fiber optic switch while reducing the insertion loss, size and power consumption thereof.
This and other objects, features and advantages in accordance with the present invention are provided by a fiber optic switch including a plurality of optical inputs and a plurality of optical outputs carried by a support. The switch includes a first plurality of rotatable reflectors each being associated with a respective optical input, and a second plurality of rotatable reflectors each being associated with a respective optical output. Also, a plurality of reflector drivers directs selected pairs of the first and second plurality of rotatable reflectors to define respective paths between the optical inputs and the optical outputs.
Each of the plurality of optical inputs and outputs may comprise a lens, an optical connector and an optical fiber. For compactness and good performance the lens may be a gradient index micro lens, although a broader range of wavelength operability may be realized with specifically designed achromatic micro lenses. In any case, the optical input and output lenses are substantially indistinguishable and tailored by manufacture to efficiently transfer a substantially collimated beam of light between the two lenses. The invention takes great advantage of the fact that free-space propagating optical beams may cross paths without interference. Also, each of the first and second plurality of rotatable reflectors may comprise a rotatable mirror, and each of the plurality of reflector drivers may comprise a motor, such as a micro-electro-mechanical (MEMs) motor for compactness. The ultimate compactness of the invention is primarily limited only by the size of the motors that rotate the mirrors, which may vary over time with the state of motor technology. Also, latchable motors may reduce or eliminate the need for electrical power consumption during static operation. The switch may also include a controller for controlling the plurality of reflector drivers to produce desired routing paths between optical inputs and outputs.
The plurality of optical inputs and outputs are preferably positioned on the support in a substantially circular pattern. The support may comprise a first support portion for supporting the plurality of optical inputs in a substantially semi-circular pattern, and a second support portion, adjacent the first support portion, for supporting the plurality of optical outputs in a substantially semi-circular pattern.
Objects, features and advantages in accordance with the present invention are also provided by a method of routing light signals in a fiber optic communication system including a plurality of optical inputs and a plurality of optical outputs. The method includes providing a plurality of rotatable reflectors each being associated with a respective one of the plurality of optical inputs and outputs, and directing pairs of rotatable reflectors to define respective paths between the optical inputs and the optical outputs.
Directing respective rotatable reflectors may comprise rotating the rotatable reflectors with a motor, and the plurality of rotatable reflectors are preferably positioned in a substantially circular pattern. Providing the plurality of rotatable reflectors may comprise positioning the rotatable reflectors associated with the plurality of optical inputs in a substantially semi-circular pattern, and positioning the rotatable reflectors associated with the plurality of optical outputs in a substantially semi-circular pattern adjacent to the rotatable reflectors associated with the optical inputs.
The fiber optic switch and method of the present invention provide an increase in channel density, a reduction in the size, lower insertion loss, a broad range of wavelength performance, higher reliability, and a reduction in static power consumption.